How to extrude as a round shape in concentrated areas?
Here's how I would go about it.

lets say we have our initial shape (mine is slightly different):



I extrude a rectangle out of each one (Alt + E , extrude along normals):



Now, I select only the long edges (this can be done quickly using the box select in x-ray):



Then, I just bevel the edges to create a circle:



Final Result:



If you want yours to be more circular, just extrude out a larger square initially.